The reproductive system is unique among the bodily systems in the complexity of the mechanisms that control it. Many classes of psychoactive drugs can disrupt aspects of these controlling mechanisms and alter reproductive function. Research on the reproductive effects of drugs has numerous methodologic and interpretive problems, and several important questions remain unanswered (Reviewed by Smith & Asch, 1987). One of the most controversial issues in the research of marihuana on reproduction has been whether this drug is estrogenic or not. In the adult uterus, a large spectrum of estrogenic responses is elicited by a variety of steroidal and non-steroidal compounds. The type(s) of response(s) and the cell-types involved are dependent upon the nature of the compound and the hormonal environment the uterus is exposed to. In this respect, progesterone remarkably alters estrogenic responses in the uterus in a cell type- specific manner. Therefore, sensitive and defined systems are essential to determine the estrogenicity of marihuana, and the problem necessitates a concerted effort from various angles. The diverse but combined expertise of the investigators present a unique opportunity to fulfill this purpose. Our specific aims are to: 1) determine the stage specific effects of delta-9-tetrahydrocannabinol (THC) on preimplantation embryo development, implantation and decidualization; 2) determine if the effects of THC are on the embryo, the uterus or both; 3) determine whether THC functions as an estrogen or an estrogen antagonist in inducing implantation in delayed implanting mice; 4) determine whether the effects of THC follow phasic estrogenic responses in the ovariectomized uterus and are modulated by progesterone; 5) determine whether THC discordantly alters the gene expression (as an estrogen) induces gene expression in the ovariectomized uterus in a cell type-specific manner that is altered by progesterone pretreatment. To determine stage and site specific effects of THC during early pregnancy, the blue dye method, embryo manipulation, culture and transfer will be employed. To determine estrogenicity of THC, the model of delayed implantation, assessment of Phase I (125I-BSA uptake) and Phase II (3H-thymidine incorporation) estrogenic responses and studies of gene expression in the uterus will be used. Expression of c-myc and IGF-I genes will be determined by detection of mRNAs by northern blot hybridization and their cell type-specific expression by in situ hybridization. Immunocytochemistry will be used to localize cell type-specific accumulation of c-myc and IGF-I proteins. The results obtained from the proposed study will not only establish whether THC elicits any estrogenic effects and interferes with early pregnancy, but will also show for the first time whether THC has any effect on gene expression in the uterus. Because in most cases pregnancy failure occurs during the peri-implantation period, the proposed experiments on the effects of THC during early pregnancy will provide important information as to the cause (embryo, uterus or both?) of pregnancy failure following exposure to the drug.